1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to an LCD with data compensation function.
2. Description of the Prior Art
In an LCD, the cost of the source driver is much higher than the gate driver. In order to reduce the total cost of the LCD, the structure of pixels sharing data lines is generated. In the structure of pixels sharing data lines, the data lines are reduced by half; in this way, the amount of source drivers is reduced, which will lower the total cost. However, due to this structure, the amount of the gate drivers will be doubled and the frequency of the gate driving signals also has to be doubled for keeping the same frame rate. In other words, the turning-on period of a gate is reduced by half. Under such conditions, the data lines cannot be fully charged or discharged to the predetermined voltage levels. Therefore, in the prior art, coupling lines are disposed near the data lines to increase driving abilities of the data lines.
FIG. 1 is a diagram illustrating coupling lines of a conventional LCD. As shown in FIG. 1, the pixel Pxy is coupled to the data line Dy and the gate line Gx, and the pixel P(x+1)y is coupled to the data line Dy and the gate line G(x+1). The left side of the pixel Pxy is disposed with a coupling line CP1, which is a metal line. In this way, a parasitic capacitor Cpd1 is formed between the coupling line CP1 and the pixel Pxy. The right side of the pixel P(x+1)y is disposed with a coupling line CP2, which is also a metal line. In this way, a parasitic capacitor Cpd2 is formed between the coupling line CP2 and the pixel P(x+1)y. The voltages on the pixels Pxy and P(x+1)y are affected by the voltages of the coupling lines CP1 and CP2. Therefore, the voltages on the pixels Pxy and P(x+1)y can be adjusted by controlling the voltages of the coupling lines CP1 and CP2; consequently, the driving ability of the data line Dy is improved.
FIG. 2 is a diagram illustrating a conventional LCD with data compensation function. As shown in FIG. 2, a coupling line is disposed between every two data lines. For example, the coupling line CP1 is disposed between the data lines D1 and D2, the coupling line CP2 is disposed between the data lines D2 and D3, the coupling line CPn is disposed between the data lines Dn and D(n+1), and so on. The coupling line CP1 is disposed between the data lines D1 and D2, and thus the pixels which are affected by the coupling line CP1 comprise pixels P21, P12, P41, P32, and so on. The coupling line CP2 is disposed between the data lines D2 and D3, and thus the pixels which are affected by the coupling line CP2 comprise pixels P22, P13, P42, P33, and so on. All the coupling lines CP1˜CPm are coupled to one common end. In this way, the voltages of all the coupling lines CP1˜CPm are controlled by controlling the voltage of the common end, and thus the voltages of all pixels in the LCD 200 will be affected by the coupling lines.
Referring to FIGS. 3 and 4, FIG. 3 is a diagram illustrating the LCD 200 adopting two-line inversion driving method, while FIG. 4 is a timing diagram illustrating the common end of the LCD 200 with coupling lines adopting two-line inversion method. In FIG. 4, T represents a period of time with a gate being turned on and the vertical axis represents a voltage level. The polarity of the voltage on the common end (compared to a common voltage level) changes in the same way as the data lines change. For example, when the polarity of the voltages of the data lines D1˜Dm is negative (compared to the common voltage level), the polarity of the voltage on the common end is also negative, and when the polarity of the voltages of the data lines D1˜Dm is positive (compared to the common voltage level), the polarity of the voltage on the common end is also positive.
Referring to FIGS. 5 and 6, FIG. 5 is a diagram illustrating the LCD 200 adopting two-line-dot inversion driving method, while FIG. 6 is a timing diagram illustrating the common end of the LCD 200 with coupling lines adopting two-line-dot inversion driving method. In FIG. 6, T represents a period of time with a gate being turned on and the vertical axis represents a voltage level. The polarity of the voltage on the common end (compared to a common voltage level) changes in the same way as a part of the data lines changes. When the two-line-dot inversion is adopted, the data lines are divided into two groups, each group having different polarity relative to the other. However, due to the couple lines connected to the common end, the polarity of the voltage on the common end only changes according to one of the two groups. For example, when the polarity of the voltages of the odd data lines D1, D3, D5 . . . Dm−1 (assuming m is an even number) is negative (compared to the common voltage level), the polarity of the voltage on the common end is negative, and when the polarity of the voltages of the odd data lines D1, D3, D5 . . . Dm−1 is positive (compared to the common voltage level), the polarity of the voltage on the common end is positive. In this way, the polarity of the voltage on the common end is not the same as the polarity of the even data lines D2, D4, D6 . . . Dm. Consequently, the driving ability of the odd data lines is enhanced, but the even data lines is reduced. This causes non-uniformity on the LCD 200, as shown in FIG. 7, and color difference in stripe shape is generated. Therefore, the conventional LCD 200 cannot adopt the two-line-dot inversion driving method.